The present invention relates to acrylic polymer compositions which are capable of rapid cure to highly tacky, creep resistant pressure sensitive adhesives and to articles of manufacture comprising films of such pressure sensitive resins. In another aspect, the invention relates to a process of manufacture of such articles. More particularly, it pertains to acrylic pressure sensitive resins and articles manufactured therefrom, containing polytitanoxanes or polyzirconoxanes.
Pressure-sensitive resins are used conventionally in the form of films to provide adhesive bonds between normally non-adhering superstrates and substrates. The films may be prepared by casting them from organic solvent solutions and evaporating the solvent. In order to increase the cohesive strength and improve the creep resistance and holding power of the dried film, metal alkoxides such as tetrabutyltitanate (U.S. Pat. No. 3,532,708) and chelated metal alkoxides (U.S. Pat. Nos. 3,769,254 and 3,886,126) may be incorporated into the solvent solutions. Upon drying, crosslinked films result by interaction of the metal alkoxide with functional groups of the pressure sensitive resin such as carboxyl or hydroxyl groups.
The solutions allow cure of the resins merely by evaporation of the solvent. Of particular interest have been tetraalkyl titanates and titanium chelates which are formulated with hydroxyl or acid containing acrylic pressure-sensitive resins in alcohol solutions to yield stable solutions from which crosslinked pressure-sensitive resins are obtained by evaporation of the alcoholic solvent. However, such titanates can cause in pressure sensitive resins a loss in tack and can impart to dried films of the resins a yellow color which minimizes the suitability of such films for use on transparent or translucent substrates. The undesirable loss in tack of the dried films is manifested by a decrease in the agressiveness or ease with which adhesive films form bonds when they are applied to substrates. The undesirable yellow coloration creates an aesthetic problem which inhibits or prevents the use of these pressure sensitive systems in polyester or polyethylene laminates and in medical tapes.